I agree with what you said. Bayern Munich is doing very well in Bundesliga so it is almost certain they will win title. Because of this really exciting challenge for Bayern Munich is Champions League where they will play against very strong teams like Real Madrid and Barcelona. Bundesliga is not as exciting because Bayern Leverkusen team that could have competed with Bayern Munich is not doing well. Champions League will show how good Bayern Munich really is and it will be interesting to see how they do against best teams in Europe.
I disagree with what you mentioned regarding Leverkusen because the two teams are six points different, and Leverkusen still has the opportunity to close the gap with the games left in the season. I also assumed that Bayern had already won the Bundesliga title this season but since they drew their last match against Union Berlin, Leverkusen might win this trophy again this season.
However, the Champions League is not the only big challenge for Bayern Munich this season, as they failed to maintain their winning way against a team in the middle of the league. Bayern Munich needs to perform at their highest level in the last few matches of the season because if they continue with a draw or lose, Leverkusen might surpass them in the league table. After all, Xabi Alonso's team has no other competition this season apart from the Bundesliga.